How do I read a 3-digit capacitor code?

A 3-digit IEC capacitor code (e.g. 104) uses the first two digits as significant figures and the third as a power-of-ten multiplier — all in picofarads. So 104 = 10 × 10⁴ pF = 100,000 pF = 100 nF. 222 = 22 × 10² pF = 2200 pF = 2.2 nF. The special multiplier digit 9 means ×0.1, so 109 = 1.0 pF.

How do I convert capacitor values between pF, nF and μF?

To convert: divide pF by 1,000 to get nF; divide pF by 1,000,000 to get μF; multiply μF by 1,000 to get nF; multiply μF by 1,000,000 to get pF. Example: 100 nF = 100,000 pF = 0.1 μF. The letter notation shorthand uses p (pF), n (nF), u or μ (μF) — so 4n7 means 4.7 nF and 100n means 100 nF.

How is energy stored in a capacitor calculated?

Energy stored in a capacitor is calculated using E = ½ × C × V², where C is capacitance in Farads and V is voltage in Volts. The result is in Joules. For example, a 100 μF capacitor charged to 12 V stores E = 0.5 × 100×10⁻⁶ × 144 = 7.2 mJ. The charge stored is Q = C × V in Coulombs.

What is the RC time constant and how do I calculate it?

The RC time constant (τ, tau) is the time for a capacitor to charge to 63.2% of the supply voltage through a resistor: τ = R × C. At 5τ (five time constants) the capacitor is 99.3% charged — considered fully charged in practice. Example: 10 kΩ × 100 nF = 1 ms time constant; the capacitor is fully charged in about 5 ms.

What is a capacitor's self-resonant frequency (SRF)?

Every real capacitor has a self-resonant frequency (SRF) caused by its equivalent series inductance (ESL). Below the SRF the capacitor behaves capacitively; above it, inductively. At the SRF, impedance is at its minimum and equals the ESR alone. SRF = 1 / (2π × √(L × C)). For bypass capacitors, always choose a value whose SRF is above your operating frequency.

What are E12 and E24 standard capacitor values?

E-series values are internationally standardised preferred numbers. The E12 series has 12 values per decade (1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2) with ±10% tolerance. E24 has 24 values (±5%), E48 has 48 values (±2%), and E96 has 96 values (±1%). Capacitors are typically available in E6, E12 or E24 series.

Capacitor Code Calculator — Decode IEC, SMD & EIA-198 Codes Instantly | CalcEngines

Electronics Calculators

Capacitor Code Calculator

Name: Capacitor Code Calculator
Author: CalcEngines

Decode IEC 3-digit codes, SMD EIA-198 markings, and letter notation (4n7, 100n, 0.1μF). Calculate energy stored, charge, RC time constant, impedance vs frequency, and nearest E-series standard values.

Advanced Capacitor Calculator

Code decode · SMD EIA-198 · Energy & Charge · Impedance · E-Series

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Capacitor Code Input

Code (3-digit IEC, letter notation, or plain pF)

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Tolerance Code

Voltage Code (EIA)

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Code Format Guide

3-Digit IEC Code

104 → 10×10&sup4; pF = 100 nF
222 → 22×10² pF = 2.2 nF
330 → 33×10° pF = 33 pF
009 → 0.9 pF (digit 9 = ×0.1)

First two digits = significant figures. Third digit = power-of-10 multiplier. Result is always in pF.

Letter / Direct Notation

4n7 → 4.7 nF
100n → 100 nF
0.1u → 0.1 μF
47p → 47 pF

p = pF n = nF u/μ = μF m = mF. The letter acts as both unit and decimal point.

Decoded Result

Capacitance

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Tolerance

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Voltage Rating

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Min Value

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Max Value

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Picofarads

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Nanofarads

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Microfarads

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μF

τ at 1 kΩ (RC)

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time constant

Nearest E12

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standard value

Value to Encode

Capacitance Value

μF

Unit

Tolerance

Voltage Code

Generated Codes

IEC 3-Digit Code

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Code + Tolerance

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Full Marking

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Letter Notation

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Scientific

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μF

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Nearest E12

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Nearest E24

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SMD Marking Input

SMD Code (EIA-198, 3-digit, or R-decimal)

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EIA-198 letter multipliers: R=×0.01 A=×1 B=×10 C=×100 D=×1k E=×10k F=×100k
Example: 22C = 22×100 = 2200 pF = 2.2 nF

Decoded SMD Value

Capacitance

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Format Detected

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IEC Equiv. Code

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μF

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EIA-198 Multiplier Reference

Letter	Multiplier	Example (sig=22)	Typical Range	Common Application
R	×0.01	0.22 pF	<1 pF	Very small / RF trim caps
A	×1	22 pF	1–99 pF	Small ceramic, RF circuits
B	×10	220 pF	100–990 pF	RF, timing circuits
C	×100	2200 pF (2.2 nF)	1–99 nF	General purpose ceramic
D	×1,000	22 nF	10–990 nF	Coupling, bypass
E	×10,000	220 nF	100 nF–9.9 μF	Filter, decoupling
F	×100,000	2.2 μF	1 μF+	Bulk storage, electrolytic

Input Parameters

Capacitance

Voltage

Series Resistance

Frequency

RC Charge / Discharge

Time (×τ)	Charge %	Discharge %	Actual Time

Results

Energy E = ½CV²

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Joules

Charge Q = CV

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Coulombs

Time Constant τ = RC

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seconds

63% Charge (1τ)

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99% Charge (5τ)

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Reactance X_c

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Ohms

Self-Resonant Freq

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Current @ Freq (1 V)

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Key Formulas

E = ½ × C × V²
Q = C × V
τ = R × C
X_c = 1 / (2πfC)

E in Joules Q in Coulombs τ in seconds X_c in Ohms

Capacitor Parameters

Capacitance

ESR — Series Resistance

ESL — Series Inductance

Real caps have ESR & ESL parasitics creating a self-resonant frequency (SRF). Below SRF = capacitive; above = inductive.

Key Values

Self-Resonant Freq

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|Z| at SRF (= ESR)

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Q Factor @ 1 MHz

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|Z| at 100 kHz

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|Z| at 1 MHz

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Impedance vs Frequency

|Z| vs Frequency — Log-Log Scale

■ Total |Z| ■ X_c ideal ■ ESR floor ··· SRF

Find Nearest Standard Value

Target Capacitance

E-Series

Tolerance by Series

E-Series & Tolerance

E6 → ±20% (M)
E12 → ±10% (K)
E24 → ±5% (J)
E48 → ±2% (G)
E96 → ±1% (F)

Higher series number = more values per decade = tighter tolerance components.

Nearest Values

Nearest Standard Value

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Error from Target

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IEC Code

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Next Below

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Next Above

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E12 Multiplication Table

E12 Base	×1 pF	×10 pF	×100 pF	×1k pF / nF	×10k nF	×100k nF / μF

How to Read Capacitor Codes

Capacitors use several marking systems depending on their size and type. The most common is the IEC 3-digit code used on ceramic, film and small electrolytic capacitors. The first two digits are the significant value and the third is a power-of-ten multiplier — the result is always in picofarads (pF). So 104 means 10 × 10⁴ = 100,000 pF = 100 nF = 0.1 μF. The code 222 means 22 × 10² = 2,200 pF = 2.2 nF.

The special multiplier digit 9 means ×0.1 rather than ×10⁹ — so 159 decodes to 1.5 pF. Optional suffix letters indicate tolerance: F=±1%, G=±2%, J=±5%, K=±10%, M=±20%. Voltage codes follow EIA-198: 1A=10V, 1C=16V, 1E=25V, 1H=50V, 2A=100V, 2E=250V.

Letter notation is common on PCB schematics and component labels: the letter acts as both the unit symbol and decimal point. 4n7 = 4.7 nF, 100n = 100 nF, 0.1u = 0.1 μF, 47p = 47 pF. The units are p (pF), n (nF), u or μ (μF) and m (mF).

SMD Capacitor Codes — EIA-198 Standard

Surface-mount device (SMD) capacitors are too small for a full label, so they use compact coding. The EIA-198 system uses two significant-figure digits followed by a letter multiplier: R=×0.01, A=×1, B=×10, C=×100, D=×1,000, E=×10,000, F=×100,000 (result in pF). For example, 22C = 22 × 100 = 2,200 pF = 2.2 nF, and 47D = 47 × 1,000 = 47 nF.

Some SMD capacitors use the R-decimal notation where R acts as a decimal point multiplied by 100 pF: R47 = 0.47 × 100 = 47 pF. Many modern SMD ceramics also use the standard 3-digit IEC code directly, particularly in larger case sizes (0805, 1206 and above).

Energy, Charge & RC Time Constant

The energy stored in a capacitor is E = ½ × C × V². A 100 μF capacitor charged to 12 V stores 7.2 mJ — enough to briefly power a small LED. The charge on the plates is Q = C × V; at 12 V that same capacitor holds 1.2 mC (milliCoulombs). Both quantities scale with the square and linear functions of voltage respectively, so doubling the voltage quadruples the stored energy.

The RC time constant τ = R × C defines how quickly a capacitor charges through a resistor. At one time constant (1τ) the capacitor reaches 63.2% of the supply voltage; at 5τ it is 99.3% charged — considered fully charged in practical circuits. A 10 kΩ resistor with a 100 nF capacitor gives τ = 10,000 × 100×10⁻⁹ = 1 ms, reaching full charge in ~5 ms.

Capacitive reactance Xc = 1 / (2π × f × C) decreases with frequency and capacitance. A 100 nF capacitor has Xc ≈ 1.59 kΩ at 1 kHz but only 1.59 Ω at 1 MHz — this is why large capacitors are used for low-frequency filtering and small ceramics for high-frequency decoupling.

Capacitor Impedance and Self-Resonant Frequency

A real capacitor is not a perfect component — it has equivalent series resistance (ESR) from lead and plate resistance, and equivalent series inductance (ESL) from lead and foil inductance. Below the self-resonant frequency (SRF) the capacitor behaves capacitively; above it, inductively — meaning a bypass capacitor actually increases impedance at frequencies above its SRF and provides no filtering benefit.

The SRF is calculated as 1 / (2π × √(L × C)). A 100 nF ceramic capacitor with 1 nH ESL has SRF ≈ 15.9 MHz. Above 15.9 MHz, that capacitor looks like an inductor, not a capacitor. For high-frequency decoupling (100 MHz+) use 100 pF or 10 pF ceramics with very low ESL, or place multiple capacitors in parallel — paralleling halves ESL and therefore doubles the SRF.

E-Series Standard Capacitor Values

Capacitors are manufactured in preferred number (E-series) values defined by IEC 60063. The E-series spacing ensures that any value within the tolerance range of one component overlaps with the next, giving complete coverage across the value range. The E6 series (6 values/decade: 1.0, 1.5, 2.2, 3.3, 4.7, 6.8) covers ±20% tolerance. E12 (12 values/decade) covers ±10%, E24 ±5%, E48 ±2%, E96 ±1%.

In practice, capacitors are most commonly stocked in E6 and E12 series. E24 is available for precision applications. E48 and E96 are rare for capacitors (though standard for precision resistors). When designing a circuit, always select the nearest E-series value and verify the actual tolerance meets your design margin — a ±20% capacitor can be up to 20% above or below the marked value.

Frequently Asked Questions

What does 104 mean on a capacitor?

104 is an IEC 3-digit code meaning 100 nF (0.1 μF). The first two digits (10) are the significant value and the third digit (4) is the power-of-10 multiplier: 10 × 10⁴ = 100,000 pF = 100 nF. This is one of the most common decoupling capacitor values used in digital and analogue circuits. It is also written as 100n, 0.1u, or 0.1 μF.

How do I decode an SMD capacitor marked 22C?

22C is an EIA-198 SMD code. The digits (22) are the significant value; the letter (C) is the multiplier. C = ×100 pF, so 22C = 22 × 100 = 2,200 pF = 2.2 nF. The multiplier letters are: R=×0.01, A=×1, B=×10, C=×100, D=×1,000, E=×10,000, F=×100,000. So 47D = 47,000 pF = 47 nF, and 10E = 100,000 pF = 100 nF = 0.1 μF.

What is the difference between pF, nF and μF?

All three are units of capacitance based on the Farad (F). 1 μF (microfarad) = 1,000 nF (nanofarad) = 1,000,000 pF (picofarad). Small ceramic capacitors for RF and signal circuits are typically measured in pF (1–999 pF). General-purpose ceramics, film caps and small electrolytics are in nF (1–999 nF). Larger electrolytics, supercapacitors and power supply caps are in μF or mF (millifarad).

How do I calculate the RC time constant?

The RC time constant τ (tau) = R × C, where R is in Ohms and C is in Farads. The result is in seconds. At 1τ the capacitor charges to 63.2% of supply voltage; at 2τ to 86.5%; at 5τ to 99.3% (considered fully charged). Example: 1 kΩ and 100 nF → τ = 1,000 × 100×10⁻⁹ = 100 μs. Fully charged in ~500 μs.

Why does a capacitor have a self-resonant frequency?

Every physical capacitor has parasitic lead and foil inductance (ESL). This ESL forms an LC resonant circuit with the capacitance. At the self-resonant frequency (SRF = 1 / (2π√LC)) the inductive and capacitive reactances cancel, leaving only ESR — the impedance is at its absolute minimum. Above the SRF the device is inductive, not capacitive. For bypass and decoupling capacitors, choose values whose SRF is above the highest frequency you need to filter.

How do I choose between capacitor tolerance codes J, K and M?

Tolerance code J = ±5%, K = ±10%, M = ±20%. For timing circuits (RC oscillators, filters) use J (±5%) or tighter to minimise frequency variation. For decoupling and bypass where exact value is not critical, M (±20%) or K (±10%) are fine and cheaper. Note that Class II ceramics (X7R, X5R) often show significant capacitance drop with DC bias and temperature regardless of the printed tolerance code — account for this in your design margin.

What are the most common capacitor values in electronics?

The most common values (from E12 series) are: 10 pF, 22 pF, 47 pF, 100 pF (RF/crystal load), 1 nF, 10 nF, 100 nF (decoupling — the ubiquitous “0.1 μF” or code 104), 1 μF, 10 μF, 100 μF (bulk supply decoupling and filtering). The 100 nF ceramic capacitor is by far the most widely used in digital electronics, placed on every VCC pin to suppress switching noise.

Calculations are theoretical estimates. Actual capacitor performance varies with temperature, voltage bias, frequency, ageing, and component tolerances. Always consult the manufacturer datasheet for your specific component.
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